TW504427B - Composition, methods and devices for high temperature lead-free solder - Google Patents

Abstract

A lead-free solder comprises an alloy of silver and bismuth in amounts of 2 wt% to 18 wt% and 98 wt% to 82 wt%, respectively. Contemplated alloys have a solidus of no lower than 262.5 DEG C and a liquidus of no higher than 400 DEG C. Contemplated alloys may further comprise a chemical element with an oxygen affinity that is higher than the oxygen affinity of the alloy.

Description

The scope of the present invention is a lead-free flux. Two, "said ^ bonding method is to use a high error containing agent to adhere to the product = conductor grains in the lead (leadframe) as a mechanical: and to provide heat between the die and the pin and Conduction of electricity. Although most of them are high in content, tinctures are relatively convenient and show various desired physicochemical properties, but t is used in the bonding of crystal grains and other tinctures-the use of lead _ 3 brothers and occupational health point of view influences. Therefore, various methods have been initiated to replace lead-containing solder with lead-free die-bonding compositions. For example, as described in U.S. Patent Nos. 5,15,195; 5,19,539; 5,25,600,600; 5,399,907, and 5,386,000, 'which uses a polymeric adhesive (e.g., epoxy resin or Cyanate resin) to adhere the crystal grains to the substrate. Polymeric adhesives can usually be cured in a relatively short time at a temperature below 200t, and as shown in US Patent No. 5,612,403, after curing, the soil retains structural flexibility so that The die-bonded integrated circuit can be attached to a flexible substrate. However, most polymeric adhesives have a tendency for resin to bleed out. This phenomenon may cause an undesired reduction of the current contact between the crystal grains and the substrate, or even cause the crystal grains to partially or completely fall off. To prevent at least some resins from oozing out, as described by Mitanoo et al. In U.S. Patent No. 5,982,041, a silicone-containing grain bonding adhesive may be used. Although this adhesive can improve the connection of the wiring At the same time, the combination of resin sealant with semiconductor wafers, substrates, and / or pins is also improved, but the curing process of at least some of these adhesives requires high energy 7; " * 1 -— __- 4 _______ This paper Zhang Shoucheng's family standard (CNsTl4 specification (210X 297 mm) ~ 504427 A7 B7 V. Description of the invention (2) The amount of radiation source makes the bonding method of the crystal grains increase the obvious cost. Alternatively, as shown in Dietz et al., U.S. Patent No. 4,459,166, glass frit containing high lead borosilicate glass is used to avoid the high energy curing process. However, most of the high lead borosilicate containing The glass paste needs a temperature of 425 ° C and higher in order to permanently fix the crystal grains on the substrate. Moreover, the glass paste tends to crystallize between heating and cooling, thereby reducing the adhesion of the adhesive layer. — Another solution The method is to adopt Use high melting point solder to bond the die to the substrate or pins. Soldering the die to the substrate has various advantages, including relatively simple operation without solvent coating, and in some examples it is relatively inexpensive. In this technique Various high melting point fluxes are known, but all or almost all of them have one or more disadvantages. For example, most gold eutectic alloys (eg, 8-11-20% Sn, Au-3% Si, Au-12% Ge , And Au-25% Sb) are relatively expensive and often impaired by less than ideal mechanical properties. Or, alloy butyl (Ag-10 ° / 〇Sb-65% Sn, for example, the United States of America Olsen) (Patent No. 4,170,472) can be used for a variety of high-flux applications, but alloy tins have a solidus temperature of 228 ° C and are also impaired by relatively poor mechanical performance. Although various are known in the art Method and composition of flux and die bonding composition, but all or almost all of them still have one or more disadvantages', so there is still a need to provide improved compositions and methods for fluxes (especially lead-free fluxes). SUMMARY OF THE INVENTION The invention relates to a method of flux Compositions and devices, which present paper _ ^ _ flux applied China National Standard Scale (CNS) A4 size (210 X 297 mm)

Binding

V. Description of the invention (= Amount: Bi, its Ag content is 2% to 18% by weight, at 262 5t, ',' 8% to 82% by weight. The alloys covered are not low, too wide The solidus temperature and ^ are higher than that of Wei Zhiye Erfa. In the state of the Ming-standard, the silver content in the alloy is 2% by weight. Double: :: 98% to 93% by weight, or, silver For content, Yindong i soil 18 weights 0/0, and bismuth is 93% to 82% by weight, or each other. .. · Each amount is 5% to 9% 0/0, and bismuth is 95% to 91 doubles; the composition covered can still include—chemical elements with higher oxygen affinity than alloy hearts, and the preferred elements include A !, Ba,,, Ce, Cs, Hf, Li, Mg, The concentrations of Nd, P, Sc, Sr, Ti, and uranine are usually in the range of about 10 ppm to about 10,000 ppm. In another example of this month, the covered agents have At least 9,…, conductivity, and measured after placing the moisture meter for one second, it shows that it is wet with Ag and wetting f0rce (about 0.2 mN). The composition covered can be formed into various shapes' including Shaped, banded, pre-shaped, spherical, or scale bonds. In another aspect of the invention, the subject, 'An electronic device contains a semiconductor die,' which is connected to a surface by the composition covered Among them, the semiconductor crystal grains specifically covered include crushed, germanium, and gallium gallium crystal grains. The present invention also covers a part of the small crystal grains or one part of the surface of the device with silver metallization. Particularly preferred The surface contains a silver metallized book leg. On the other hand, the covered flux is used in an area array electronic package, which forms a plurality of bumps on the semiconductor die as the die. Current between package substrate (commonly referred to as flip chip) or printed circuit board (commonly known as paper size standard (CNS) A4 specification (210X297)) -6 «A7 B7 V. Description of the invention (4 called wafer board) Alternately, the fluxes covered can be used in the He-Group ¥ flux ball to connect the package to the substrate (commonly known as ban grid aray, there are many variations depending on the subject) or to connect the die to Substrate or printed circuit board. In another aspect of the invention, the method for manufacturing a flux composition has a step, wherein the content of bismuth and silver provided is 98 to 82% by weight and 2 to 18% by weight, respectively. The next step Here, silver and bismuth melt at a temperature of at least 960 ° C to shape an alloy whose solidus temperature is not lower than 262.5t and liquidus temperature is not higher than 400t. The methods covered are still Including the addition of chemical elements with oxygen affinity higher than the oxygen affinity of the alloy as needed. K The following detailed and preferred embodiments of the helmet and the detailed description accompanying the drawings will better show the various items of the present invention , Features, appearance, and excellent! Brief description Figure 1 is a schematic longitudinal section of an exemplary electronic device. Detailed description The inventors have discovered (especially for the desired properties) that the group covered; in the application of a variety of die bonding, it is extremely advantageous to replace 高 with high: mis-soldering flux. In particular, the composition covered is an alloy that does not contain the wrong alloy, and has a thickness of 2.60 (: "Solid Phase Temperature (and preferably not lower than sinking) and a liquid that is not high at 400 ° C. Phase line temperature. 'The composition covered is binary and its silver content is 2% by weight to 1 8. In the particularly preferred aspect of the present invention, gold, far yuan alloys can be used for flux and

1% by weight and the bismuth content is 98% to 82% by weight. In the method for preparing the covered compositions, a suitable weight (as described above) of pure metal is placed in a strong or resistant binary state (such as a graphite crucible) and heated under vacuum or inert gas pressure (such as nitrogen or helium). To 960 ° C. and 1000 t: until a liquid solution is formed. Stir and hold at its temperature to allow sufficient time to ensure that the two metals are fully mixed and melted. This molten mixture is quickly poured into a mold to cool to the surrounding temperature to solidify, and then made into a linear shape (including heating materials in to, 190 C) by conventional technology, or made into a strip-like method. The rectangular wide plate is annealed to 225-25 ° C, and then hot rolled at the same temperature. Alternatively, the strip can be extruded and rolled into a thinner inch. The melting step can also be performed in air. // The slag to be formed is removed before the mixture is poured into the mold. 4. In another aspect of the subject of the present invention (especially when a higher liquidus temperature is required), the composition it covers may be Ag is included in the alloy in an amount of 7 wt% to 18 wt% and bismuth is 93 wt% to 82 wt%. On the other hand, when a relatively low liquidus temperature is required, it covers The composition may include Ag in the alloy in an amount of 2% to 7% by weight and bismuth in an amount of 98% to 93% by weight. However, the composition generally used in most grain bonding applications is in the alloy. , The amount of Ag is 5 weight% to ⑺ weight ^ / ❶ and ... is "weight% to 90 weight%. It is particularly understood that the covered composition can be used as a lead-free flux, and this flux is completely free of, and is considered to be the main component common to lead-free solder & The most suitable composition covered is a binary alloy, but it should also be understood that its alternative composition can be described in the invention (a quaternary, and more Nanyuan alloy. Pro-ΓΓ, 'particularly suitable alternative composition can include —One or more kinds of chemical elements with oxygen affinity that are lower than the oxygen affinity of the alloy. The elements include A ,,,,,,, and ^^, which are converted to ρ. Π c Le Cs Hf, h, Mg, Nd, No .: Two Tl, Y, and ZΓ ', which are still included in the alloy,' Chen Youliwan? Da, about 10 Peng and about 1000 PPm. Although not want to be connected with special = theory or mechanical transfer However, it can be noted that it is higher than the alloy ^ :: Wusu can reduce metal oxides. Known metal oxides can increase rubber ^ or ^ melting flux, surface tension), so what is covered by the present invention is减） Metal # ι 化 的 时时 通通 f will reduce the surface tension of the bright flux, so it is obvious Added the wettability of the flux. In another example, one or more metals can be added to improve the thermal-mechanical properties of the solder without the wrong flux (for example, thermal conductivity, thermal expansion coefficient, hardness, pasty field, Ductility, etc.). Metals covered by the special collection include ... Indium, tin, #, zinc, and nickel. However, various metals other than the aforementioned metals are also suitable for use in the technology herein, as long as such metals are improved At least one thermal-mechanical property. Therefore, the metals that can be covered include: copper, gold,

Germanium, and Kun. Therefore, the metals specifically covered include A% to 18% by weight ... the amount is 98% by weight to 8 /% by weight; lining = prime, and f is from 0.1% to 5.0% by weight. The third element specifically covered includes at least one of Au, Cu, Pt, Sb, In, Sn, Ni, Ge, & MZn. Therefore, with the specific amount of the third element, it should be recognized that the alloy has a solidus temperature of not less than 230 C (preferably not less than 248 °, and most preferably not less than 258 ° C), And no higher than the liquidus temperature of 400 arts. This paper size applies to the Chinese National Standard (CNS) A4 specification (210X 297) -9-504427 A7 B7 V. Description of the invention (7) The uses specifically covered by the alloy include the bonding of grains (for example: bonding Connect the semiconductor die to the substrate). Accordingly, the present invention encompasses an electronic device that will include a semiconductor die attached to a surface via a substance that contains a composition containing the ternary (or higher) alloy covered. Regarding the production of the covered ternary alloys, they have the same considerations as described in the applications described above. Generally, it is covered that the third element is added to the binary alloy or the components of the binary alloy in an appropriate amount. It should also be understood that the addition of chemical elements or metals to improve one or more physical-chemical properties or thermal-mechanical properties can be performed in any order, as long as all components in the alloy are substantially complete (for example: each One component is at least 95%) molten, and the present invention covers that the order of addition is not limited to the subject matter of the present invention. Similarly, it should be understood that although it is preferred that silver and bismuth be combined before the melting step, the present invention also covers that silver and bismuth can be melted separately, and the molten silver and bismuth can be combined. The heating step is further extended to a temperature above the melting point of silver to substantially determine complete melting and mixing of the components. In particular, it should be understood that when one or more additional elements are included, the solidus temperature of the alloys covered will decrease by j °. Therefore, covered alloys with added elements will have 260-255 ° C, 225-250 ° C, 250-245 ° C, 245-235 ° C, and even lower solidus temperatures. Regarding the thermal conductivity of the covered alloys, the subject composition according to the present invention has a thermal conductivity of not less than 5 W / mk, preferably it is not less than 9 W / mk, and the best is not less than 1 5 W / mk. The present invention also covers suitable compositions including alloys with wettability, the wettability of which is higher than 0.1 mN with silver, preferably higher than 0.2 mN, and most preferably higher than 0.3 mN. -10-_ This paper size applies to China National Standard (CNS) A4 (210 X 297 mm)

Binding

^ U4427 A7

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504427 A7 ____B7 5. Description of the invention (9) is greater than 260 C. Particularly good alternative uses include joining the components of a heat exchanger with a covered flux, which serves as a non-melting isolation ball or a current / thermal energy connection. Example Since the thermal expansion coefficients of various substances are different, solder joints are often subjected to a shear load. Therefore, it is particularly necessary to alloy these low-shear modulus materials so that they can have good resistance to thermal mechanical fatigue. For example, in the application of die bonding, having 祗 · shear modulus and good thermo-mechanical fatigue can help prevent chip breakage, especially when relatively large particles are connected to a solid support. Based on the known elastic modulus of pure metal, Ag and Bi show the miscibility of some solids, and the Ag-Bi system does not contain intermediate metal or mesophase. The present invention covers: the shear modulus of the Ag-Bi alloy at room temperature is 1 3-1 6 GPa (assuming that the shear modulus at room temperature is additive, that is, the rule of mixture) . The alloys covered have a shear modulus of 1 3-1 6 GPa at room temperature, compared with alloys Au-25% Sb and Au-20% Sn with a shear modulus of 25 GPa, especially The same method and the same assumption calculation), compared with a butyl alloy (Ag-10% Sb-65% Sn) with a shear modulus of 2 1 GPa, it is also excellent. The measured value of the shear modulus of the alloy butyl is 22.3 GPa. The test assembly using A g-89% Bi alloy to connect the silicon crystal grains to the pins after 15,000 heat aging cycles showed no signs of damage. This supports the calculation and observation of A g with low shear modulus. -B i alloy. In the application of test assembly and other die bonding, the flux is usually made into a thin sheet and placed between the die and the substrate to be soldered. Subsequent heating will dissolve

Five invention description

Wire, integrated, or h substrate is heated first, and then a thin sheet is placed to be used as a connector for area array packaging. Produce a lot of & week, person, # + 70% "paste, or other forms of solder can be used for 1 =:;: ^ similar to inkjet printing; == evaporation from solid, form; for manufacturing joints. — To create an array of tincture bumps, use ^ l "#i (flux) 4 ^ # J ^ (The ball is held in place until it is the second flux ::: make :! one degree 'or two == paste, #Connection can be lower than the dazzling point of the ping agent. Use ping agent or tan agent to heat and the package of «ΙΓ ball is aligned with the array of substrates on the substrate and the half-body die is bonded to the package or printed circuit board. The best materials include Huai'an. The bumps are generated by printing solder paste through the mask, evaporating the flux through the mask, or bonding the flux to the array of conductive ridges. According to this technology, the bumps or tubes are generated. Columns can have a homogeneous composition, so when a temple or a post melts to form a joint; or the vertical direction on the surface of the semiconductor crystal grains is uneven, so only some of the bumps or columns melt. Therefore, the specific embodiments and applications of lead-free solder have been disclosed, but 'for those skilled in the art, it should be clear, except that 504427 A7 B7 five invention descriptions have been described (11

In addition, many amendments that do not depart from the concept of the present invention are also possible. In addition to the core part of the scope of the attached patent application, the subject matter of the present invention is limited. Furthermore, in the scope of the description and patent application, ^ and 疋 should not be explained in the broadest way in order to harmonize with the context. There are terms or steps, which means that the related elements, components, or steps can be presented as ', two-component, or with other yuanxin, king' or not specifically indicated, or used, Beijing, and, or steps Combined. This paper size applies to China National Standard (CNS) A4 (210X 297 mm) • 14-

Claims (1)

504427 ABCD VI. Application for patent scope 1. A composition comprising: a flux comprising an Ag content of 2% to 18% by weight / ° and a B i content of 98% to 82% by weight An alloy in which the alloy has a solidus temperature of not less than 262.5 ° C and a liquidus temperature of not more than 400 ° C. 2. The composition according to item 1 of the patent application range, wherein the Ag content in the alloy is 2% to 7% by weight, and the Bi content is 98% to 93% by weight. 3. If the composition-item in the first item of the patent application range, wherein the Ag content in the alloy is from 7% to 18% by weight, and the Bi content is from 93% to 82% by weight. The composition of item 5, wherein the alloy has an Ag content of 5% to 10% by weight, and a Bi content of 95% to 90% by weight. 05. The composition according to item 1 of the patent application range, wherein the flux It has a thermal conductivity of not less than 9 W / mk. 6. The composition according to item 1 of the patent application range, wherein the flux has a wetting force of about 0.2 mN to A g, which is measured by a wet tester for 1 second. 7. The composition according to item 1 of the patent application scope, which further includes chemical elements having an oxygen affinity higher than that of the alloy. 8. The composition according to item 7 of the scope of patent application, wherein the chemical element is selected from the group consisting of Al, Ba, Ca, Ce, Cs, Hf, Li, Mg, Nd, P, Sc :, Sr, Ding, Y, and Zr. 9. The composition according to item 8 of the scope of patent application, wherein the concentration of the chemical element is -15- The paper size is suitable for wealth ® S family standard (CNS) A4 specification (210 X 297 mm) ~ '----- ~~ ----- J 504427 A8 B8 C8 _____D8 _ 6. The scope of patent application is 10 ppm to 1000 ppm. 10. The composition according to item 1 of the scope of patent application, wherein the alloy can be formed into at least one of the following: wire-like, ribbon-like, 、 -like, positive, spherical, 'paste-like, and evaporated metal flakes. 11. An electronic device comprising a semiconductor die attached to a surface by a substance, the substance including a composition as claimed in item 1 of the patent application scope. 12. The electronic device according to item 11 of the patent application scope, wherein at least a part of the semiconductor crystal is metalized with Ag. 13. The electronic device according to item i of the patent application scope, wherein the surface is at least partially metallized with Ag. 14. The electronic device according to item 11 of the application, wherein the surface includes a lead frame made of silver metallization. 15. —A method for manufacturing a flux composition, comprising: preparing Ag and Bi, wherein the content of Ag is 2% to 18% by weight and the content of 8% is 98% to 82% by weight; And melting the Ag and Bi to a temperature of at least 960t to form an alloy, the alloy having a solidus temperature of not lower than 262.5 and not higher than 400. (: Liquidus temperature. 16. The method according to item 15 of the patent application, wherein Ag and Bi are combined before melting Ag and Bi. 17. The method according to item 15 of the patent application, which also includes Add chemical element with oxygen affinity higher than that of alloy. 18. The method according to item 15 of the scope of patent application, wherein the content of Ag is 2% to 7% by weight, and the content is 98% by weight to 9 3 Weight 0 / 〇. -16- This paper size is applicable to Chinese National Standard (CNS) A4 specification (210X297 mm) 50442Ί 8 8 8 8 AB c D 6. Application scope of patent 19. If applied, the scope of patent is the first. The method according to item 15, wherein the content of the ag is from 7 to 18% by weight and the amount is from 93% to 82% by weight. 20. The method according to claim 15 of the patent scope, wherein the ag The content is 5% to 10% by weight and the content is 95% to 90% by weight. 21. A composition comprising: a diluent, which includes an Ag content of 2% to 18% The content of Bi is 98% by weight to 82% by weight, and the content of the third element is 0.01% by weight to 5.0% by weight. 〇 的 Alloy. _ _ Wherein the third element is selected from the group consisting of: VIII, (: 11,? 81), 211, 111, 811, 1 ^, and 〇6, and wherein The alloy has a solidus temperature of not less than 230 ° C and a liquidus temperature of not more than 400t: 22. If the composition of the scope of application for item 21 of the patent application, the alloy has not less than 248 ° C solidus temperature. 23 · If the composition of the scope of the patent application No. 21, wherein the alloy has a solidus temperature of not less than 258 ° C. 24 · The combination of the scope of the patent application No. 21 The composition of the third element is Au 〇25. The composition of the 21st scope of the patent application, wherein the third element is Cu 0 26. The composition of the 21st scope of the patent application, wherein The third element is Pt. 27. The composition of the 21st item in the scope of patent application, wherein the third element is S b 〇-17- This paper size is applicable to the Chinese National Standard (CNS) A4 specification (210 X 297 mm) 504427 8 8 8 8 AB c D 6. Apply for a patent scope 28, such as the composition of the 21st patent application scope, where the third yuan Is Z η 〇29. If the composition of the scope of application for the patent No. 21, wherein the third element is I η 〇30 · The composition of the scope of the application for the patent No. 21, wherein the third element is S η 0 31. If the composition of the scope of patent application No. 21, wherein the third element is N i 0-32. If the composition of the scope of patent application No. 21, where the third element is G e 〇33. An electronic device comprising a semiconductor die connected to a surface by a substance, the substance including a composition as claimed in item 21 of the patent application scope. -18- This paper size applies to China National Standard (CNS) A4 (210 X 297 mm)